Hydraulic clutch problems, HELP!!!

dieseldoc · September 12, 2006

Does anyone have any tricks to bleeding the hydraulic clutch system. I am working on a 90' F-250 7.3idi and a five speed. It came in with the clutch pedal not returning all the way and very hard to push. Cust. installed a slave cylinder himself. I found the throw-out bearing binding on the input shaft. Installed new throw-out bearing and smoothed out the input shaft collar. Once together the pedal was much easier to push but still only had a 1/4 of the stroke it should. Found the master cylinder failed. Installed new master cylinder and bled following the procedure exactly like it said. Pedal now has half the stroke it should. However it will not return all the way on its own, and pedal feels spongey like air is trapped. I have tried bleeding it several times with no success. Any tricks to bleeding these clutches or other causes? Installed a new clutch and updated to the luk single mass flywheel when I replaced the throw-out bearing. Sorry for the long post but wanted to give all the facts. Thanks in advance

Keith Browning · September 12, 2006

It's probably too late now but I have always assembled and bled the hydraulic system on the bench. I take the slave cylinder and try to fill it before installing and securing the hose. I do remember having to exercise the clutch a lot and at first you may need to pull the pedal up. I have even tried an old master cylinder cap modified with a vacuum port to apply a vacuum to the system to evacuate the air similar to how you would with a P/S system. The key here is patience.

Having fought with many of these in the past, we have sold and installed the pre-assembled and purged master, line and slave assembly.

Mekanik · September 12, 2006

There is not much fluid in the clutch system, so I will usally gravity bleed them, and then have someone pump up the pedal ONE time and then open the bleeder screw. Check the pedal assy. I have replaced a ton of pedal assys. because either the shaft that snaps into the master is worn out or the shaft up top inside the bracket is loose. Check for movement while depressing the clutch. Good Luck

dieseldoc · September 12, 2006

Thanks for the ideas. I just went through the pedal assy. Because it was broke and the plastic bushings were shot. The new master came with a new rod. There isnt much slop in the linkage pieces in the cab. I will try putting a fitting in the old master cap and try that. I guess all I can do is just keep pumping the pedal. What the hell I already have an hour into bleeding the damn clutch. I wish I had researched some and gottent the whole assy. Like ford doctor said. Is it possible that since the pedal was so hard to push before that the slave cylinder was damaged? Thanks for the help guys, I have been pulling my hair out with this one.

ktmlew · September 12, 2006

If it has a strap holding the push rod collapsed release it & fill the slave with fluid before you connect the line. Then when you push the rod in it will allow the air to perk up thru the MC.

sajeev · December 22, 2009

i had such problems in the past. The easiest way is to

purge air through the clutch master cylinder reservoir

by connecting it to a hand vacuum pump .Apply vacuum

with 3/4 filled reservoir & pump clutch pedal the trapped

air in the mastercylinder will be reverse purged

through the reservoir. This can be done in 5 minutes. The

normal bleeding should be done before vacuum assisted bleed.

The air dosnt come out completely by manual bleed because the

master cylinder is installed slightly in inclined position.

mrbudge · December 23, 2009

Did you check the firewall where the master is bolted to see if it is cracked, bent, or flexing when pushing down on the pedal?

On those old external slaves I usually take them off the trans and tip them down so the line pointing up, then push the slave piston in and out a few times, the air bubble usually comes out at the master. Make sure there are no dips in the line that will trap air.

Brad Clayton · December 24, 2009

This thread is over 3 years old, I'm hoping he's moved on to newer projects. Posted Image

mrbudge · December 24, 2009

Is three years too long to spend bleeding a clutch?

Brad Clayton · December 24, 2009

dieseldoc · December 26, 2009

Most definitley moved on to other projects. I learned a valuable lesson on that project and sell the whole assembly now. Thankfully that problem unit was my brothers rig, it took two weeks of bleeding a couple times everyday to get it to work right. Have done several clutch jobs since and no troubles anymore.

LARRY BRUDZYNSKI · December 28, 2009

So....Clutch master cyl. kit plus....Rod and new bushing????

hitechmech · December 31, 2009

I know it's an older post but removing the slave cylinder since it's external and allowing it to fully extend and slowly pushing it back in with cap of master allows air to escape usually only takes about 5 or 6 extensions and reassemble pump up a few times and good to roll

sixturbosix · January 3, 2010

Vacuum bleed with hand operated vacuum pump.They usually have a little hole on top of cap.I use a basketball inflator to stick in hole.Don't fill resevoir to high when bleeding or it will suck fluid into pump.Apply vacuum and work pedal a few times then release vacuum.Do this 2 or 3 times and it's bleed.About 5 to 10 minutes of work and you are done.

Keith Browning · January 3, 2010

Vacuum bleed with hand operated vacuum pump.They usually have a little hole on top of cap.I use a basketball inflator to stick in hole.Don't fill resevoir to high when bleeding or it will suck fluid into pump.Apply vacuum and work pedal a few times then release vacuum.Do this 2 or 3 times and it's bleed.About 5 to 10 minutes of work and you are done.

Now that you mention it, I used to have an extra reservior cap that I rigged up to pull a vacuum on the system and it did work. Not perfectly all the time but I was usually able to at least "get a pedal" and from there the air worked it's way out during use... sometimes a second round with vacuum was needed though on tough ones.

These days I think most people are replacing the entire assembly which you can buy pre-assembled, filled and purged... at least on the F650/750 trucks they hydraulics are available that way. Been a loooong time since I have done any clutch work on a smaller truck.